Analog-to-digital converters have been used in a variety of applications and fields of technology, such as sensor applications, to provide an effective way of converting analog signals into digital signals. The effectiveness of the analog signal to digital signal conversion is critical in gathering accurate readings from the sensor. Moreover, many sensor applications require the outputs to be differential so as to reject common mode noise sources.
In these applications, not only is an analog-to-digital converter needed, but a specific signal is needed to drive the sensor. The sensor then generates the analog input signal for analog-to-digital conversion. The providing of the specific signal is generally referred to as a signal conditioner for the transducers.
To realize this requirement, conventional systems have often used a bridge configuration to get a zero output with no stimulus to the sensor.
An example of a conventional bridge configuration sensor system is illustrated in FIG. 1. As illustrated in FIG. 1, a second order modulator 20 is connected to two nodes of a bridge circuit 10. Moreover, a digital-to-analog converter 30 is connected to the two remaining nodes of the bridge circuit 10.
The bridge elements can be resistive, capacitive, or inductive, depending on the type of sensor. The drive signal from the digital-to-analog converter 30 should be differential, so the output common mode is constant. Making one side of the drive zero volts with a bipolar [−V to +V] drive range for the other side makes the common mode voltage constant. However, this environment is difficult to realize when using a single supply part.
Although conventional systems have used bridge configurations with some form of signal conditioning, these conventional systems have not provided the high accuracy needed in many applications. For example, in energy metering applications, high accuracy is a key requirement. To meet this need, conventional energy metering systems include a microprocessor unit to provide the signal conditioning. However, since high accuracy results require considerable signal processing on a continuous basis, the signal processing requirements are not easily coded as software loops, thereby resulting in degraded accuracy or high costs of implementation.
Therefore, it is desirable to provide a sensor system that includes high performance continuous basis signal conditioning. Moreover, it is desirable to provide a sensor system capable of converting analog waveforms to digital samples for digital processing to recover the required information, and at the same time provide a digital-to-analog converter to provide signal-conditioning so that the digital signal processing of the sensor system can synchronize the processing of both signals. The synchronization of both signals also enables other functions to be implemented efficiently, such as calibration and noise reduction, without requiring significant efforts of coding.